This invention relates to methods and systems for protecting digital data, such as multi-media presentations, digital video presentations, and vendored software to be installed, from unauthorized copying.
The rapid increase in digital methods of recording and distributing data has made it difficult for owners of copyrights on such data as images, audio recordings, and software programs to enforce their rights regarding that data. Specifically, it has become very easy for people to illegally produce and redistribute high-fidelity copies of the data.
Traditionally, the primary tool used to enforce copyrights is encryption, or scrambling. Here, data is modified in such a way that the data is useless without special descrambling hardware or software, as well as scrambling keys, possession of which indicates a right to use the data. For example, movies on digital versatile disks (DVD""s) are scrambled using keys that are hidden in the lead-in area of the disk. The keys should only appear on original, factory-pressed disks, so only, the owners of such disks have the ability to descramble and view the movies.
One of the principal weaknesses of this tool is that the protection must be removed before the data can be used (i.e. the data must be descrambled). If a person who is not authorized to make copies of the data is able to insert a recording device after the descrambler, an unprotected and descrambled copy of the data can be made, and distributed to others who also do not have the right to use the data (e.g. have not paid for a factory-pressed disk, and, consequently, have not paid any royalty to the copyright owner). Similarly, such perfect, illegal copies can also be distributed by an unauthorized distributor who succeeds in xe2x80x9cbreakingxe2x80x9d the scrambling by developing a method of either identifying the keys (e.g. reading the lead-in area of a DVD) or descrambling without a key.
The present invention helps protect descrambled data in a single, but important, context: the use of these illegal copies on legitimate or compliant devices which can also use legal, scrambled data. A compliant device is a device which detects the key in the data before the data can be used in conjunction with the device. For example, a movie with a key recorded on a DVD is placed into a compliant player. The player will detect the key and then descramble the subsequent data to enable viewing of the movie. The invention represents a modification, or addition, to the basic method of data scrambling which causes descrambles to render illegal copies of data useless. This is important since most consumers of data will own only one device for using the data, and, if that device contains a descrambler designed according to the present invention, it will be incapable of using illegal copies. Thus, the market for illegal copies is substantially reduced.
The present invention protects data from unauthorized copying. The data can be uncompressed or compressed, such as in the form of MPEG Multimedia data. The protection is accomplished by the legitimate device searching for and detecting a trigger signal, preferably in the form of a digital watermark or other steganographic embedded data in the data. If the embedded watermark or other steganographic data is present, the data is considered to be a scrambled copy. The device itself makes no distinction between authorized and unauthorized data, but descrambles the input data if a trigger signal is detected, without regard to the copy of the data being authorized or unauthorized. Thus, for unauthorized copies that contain a trigger signal with unscrambled data (the most common form of unauthorized copy) the descrambler will render the data useless.
The effect of the method and system of our invention is to rescramble an unauthorized version of the data, but descramble an authorized version of the data. This is done using the trigger signal. One property of the trigger signal is that it is preserved through signal transformation, such as one or more of compression, decompression, analog to digital conversion, and digital to analog conversion.
The trigger signal is embedded into the data in the manner of inserting a digital watermark into data to form watermarked data. The use of digital watermarking techniques to embed the trigger signal is preferred because a trigger signal inserted this way is capable of being detected even after the watermarked data is subject to signal transformation. The watermarked data is passed through a descrambler, where the trigger signal, i.e. watermark, if present; is extracted. A descrambling key and a descrambling algorithm are applied to the data if the trigger signal is present, but are not applied to the data if the trigger signal is not present.
In the present invention, data that is to be protected, such as software, images, audio, or video, is scrambled, and is also modified to contain an embedded signal, or xe2x80x9ctriggerxe2x80x9d signal to indicate that the data has been scrambled. The scrambling is performed in such a manner that the embedded signal can be detected in both scrambled and descrambled data. Any device or piece of software that is to use the data must test for the embedded signal to determine whether or not the data should be descrambled, and apply the appropriate descrambling algorithm if the signal is found. The result of this invention is that, if descrambled data is illegally copied and subsequently played in a legitimate device, the embedded trigger signal will activate the descrambler, which will then render the data unusable (since xe2x80x9cdescramblingxe2x80x9d data which is not scrambled in the first place produces unusable results). Variants of the invention include embedding descrambling keys in the data, hiding keys on physical media, and using media xe2x80x9cfingerprintsxe2x80x9d, such as patterns of bad sectors on a hard disk, as keys.
A principal object of the present invention is therefore, the provision of protection of data from unauthorized copying.
Another object the invention is the provision of a trigger signal embedded into data to be protected so that upon detection of the trigger signal only authorized copies of data may be rendered useable.
Another object of the invention is provision of a trigger signal for use in copy protection where the trigger signal is embedded into data in such a manner as to be unaffected by subsequent processing of the data containing the trigger signal.
Further and still other objects of the invention will become more clearly apparent the following specification is read in conjunction with the accompanying drawing.